Sweep signal generating system



1962 D. o. COCHRANE 3,048,788

SWEEP SIGNAL GENERATING SYSTEM Filed Aug. 15, 1958 zzvmvron. flag/ms Oliver (2255mm? BY, w 2,

ATTORNEYS Patented Aug. 7, 1962 hoe 3,048,788 SWEEP SEGNAL GENERATHNG SYSTEM Douglas Oliver Qochrane, Dorchester, Mass., assignor t Edgerton, Germeshausen and Grier, Inc., Boston, Mass, a corporation of Massachusetts Filed Aug. 15, 195-8. Ser. No. 755,261 10 Claims. (Cl. 328-180) The present invention relates to sweep circuits and, more particularly, to electronic circuits adapted to generate sweep outputs suitable for deflecting cathode-ray and similar chargedparticle beams.

The art is replete with sweep circuits of differing configuration employed for generating deflection voltages or currents for use in cathode-ray and similar apparatus to deflect the electron beam. Single-ended and push-pull circuits have been evolved employing different types of electron and gaseous-discharge tubes. It has been discovered, however, that improved operation, for the purposes later explained, may be obtained with the aid of novel sweep-circuit configurations embodying electron tubes of the type having a secondary electron-emissive electrode as one of the electrodes within the tube.

An object of the present invention, accordingly, is to provide a new and improved sweep circuit embodying tubes that employ an internal secondary electron-emissive electrode.

A further object is to provide a new and improved sweep circuit.

Other and further objects will be explained hereinafter and will be more particularly pointed out in connection with the appended claims. In summary, the invention relates to the employment of a multi-electrode electron tube having a pair of electrodes which serve as an anode and a secondary electron-emitting electrode. Sweep capacitor means is connected in a circuit to one of the said pair of electrodes and means is provided for holding the other electrode of the said pair at substantially constant potential during the passage of current through the tube and in the said circuit including the capacitor and the said one electrode of the pair. A preferred pushpull arrangement is hereinafter set forth, as are the desired circuit details.

The invention will now be described in connection with the accompanying drawing, the single FIGURE of which is a schematic circuit diagram of a preferred form of the invention.

Referring to the drawing, the tubes of a pair of electron tubes 1 and 1' embody respective primary-electronemitting cathode electrodes 3 and 3, control-grid electrodes 5 and 5, screen-grid electrodes 7 and 7, beamforming electrodes 9 and 9, anode electrodes 11 and 11', and secondary electron-emitting dynode electrodes 13 and 13' disposed adjacent to the respective anodes 11 and 11'. For reasons later explained, the electrical connections to the tubes 1 and 1, are not the same. Both of the cathodes 3 and 3' are shown connected to the B- or grounded terminals of the anode potential source B+, B-, the positive terminal B+ of which is connected through anode resistor 15 to the anode 11 of the tube 1, and through resistor 15 and connector 17 to the anode 11' of the tube 1'. The term ground as used herein, is intended to connote not only actual earthing, but also any other reference potential, such as chassis potential and the like.

The beam-forming electrode 9 of the tube 1 is shown grounded and the control-grid electrodes 5 and 5' are connected through respective resistors 19- and 19' to a common input terminal 4. A preferably grounded input terminal 6 may also be provided coaxially disposed with respect to the input terminal 4. The input terminals 4 and 6 may apply between the respective control grids 5 and 5' and the corresponding cathodes 3 and 3 of the tubes 1 and 1', input pulses I from a source of triggering pulses that are to initiate the sweep voltages desired in accordance with the present invention. The tubes 1 and 1 may, for example, be of the EFF-60 type, and the voltage source B+, B may be of the order of 500 volts.

In order to insure the proper polarity and range of amplitude of the input voltage applied to the control electrodes 5 and 5', Zener-type diodes D and D may be provided, respectively connected through resistors 21 and 23, to the opposite bias voltage sources indicated by the positive terminal 25 and the negative terminal 27. The diodes D and D may, for example, be of the 652C5 type and 653C9 type, respectively, being oppositely poled. The diode D is connected between ground and, through a resistor 29, the point P. A by-pass capacitor 12 shunts the diode D The point P, in turn, is connected to the input terminal 4. The ground terminal, of course, connects with the other input terminal 6. The diode D is also connected between ground, and through a reversely poled further diode D to the point P. The upper terminals of the respective diodes D and D will thus be oppositely biased, the diode D being biased, for example, at a potential of the order of plus five volts, and the diode D being biased at a potential of minus eight volts, thereby to hold the point P within the desired polarity and amplitude restrictions.

It will conduce to explanation if the sweep circuit asso ciated with one of the pair of tubes 1 and -1' is first described. For this purpose, it is preferred to treat with the tube 1. The screen-grid electrode 7 of the tube 1 is decoupled to ground through a capacitor 31 and is supplied with screen voltage through a circuit traceable from a resistor '33 through a potentiometer 14, a pair of resistors R and R a switch S and, by way of conductors 4 and 17 and resistor 15' to the B+ terminal. It should be observed that the screen electrode 7 of the other tube 1' is connected by the tap 39 of potentiometer 37 and a resistor 35 to the potentiometer 14, also, so that a common source of screen voltage is employed for both tubes, adjustable by adjustment of the potentiometer 14. The screen grid 7' is similarly decoupled by a capacitor 10. The secondary electron-emitting dynode 13 of the tube 1 is connected by conductor 47 through a resistor 49 and a potentiometer 49 to positive terminals 51 of difierent potential, which supply the necessary operating potential therefor. The lower potential terminal 51 may, for example, be of the order of volts positive, while the upper terminal may be of the order of volts.

The conductor 47 is also connected to a further condu-ctor 53 which connects with a switch S. The switch S, in turn, connects with any of capacitors C C C C or C the opposite terminals of which are grounded. The capacitors C through C are the sweep capacitors of different values depending upon the time constant of sweep desired. A vacant switch terminal 55 may provide stray capacitance C illustrated dotted, for a very small sweep time constant, say, of the order of ten millimicroseconds. The large capacitor C on the other hand, may produce a sweep of the order of five microseconds. The sweep capacitor C will, of course, charge in the circuit traceable from ground through the capacitor C the switch S, through conductors 53 and 47, through the space between the second electron-emitting dynode 13, and the anode 11 of the tube 1, and through resistor 15 to the B+ anode supply terminal. When a positive trigger pulse I is applied upon the control grid 5 by feeding the same to the input terminals 4 and 6, the tube 1 may be caused to conduct causing the sweep capacitor C to discharge from the secondary electron- I emitting dynode 13 through to the cathode 3, thus prod ucing a positive-going sweep voltage V that is fed by output coupling condenser C to one of the deflection means of a cathode-ray tube and the like. It is necessary, however, that during this discharge, the secondary electrons that also reach the anode 1-1, do not cause efiective variation of the anode potential. To this end of holding the anode electrode 11 at substantially constant potential during the passage of current in the tube 1 and in the discharge circuit including the capacitor C and the secondary emitting electrode 13, a high-frequency bypass capacitance 57 is provided connected between the anode 11 and ground. This by-pass 57 has the effect of extending the voltage swing of the anode 11 and is particularly advantageous for short-time constant sweeps, as before mentioned The other electron tube 1, however, is somewhat differently connected. Its anode 11 is connected by the beforementioned conductor 4 to the switch S that may be ganged with the switch S, as indicated by the dotted connection therebetween. From the switch S, the connection continues to the respective sweep condensers C C C C C and C the latter of which, like capacitance C is shown dotted to indicate stray capacitance for the shortest sweep. In such case, it is important to insure that the dynode 13 does not appreciably alter its potential during the discharge of the capacitor C through the tube 1 between the anode 11 and the cathode 3. To this end, the dynode electrode 13, which receives its operating potential through the resistor 6, conductor 41 and potentiometer 45, the latter of which is connected between positive terminals 43 that may correspond to the terminals 51, before-mentioned, is provided with an appropriate shunt capacitance 8 to ground. This capacitance 8 must be larger than any of the capacitors associated with the switch S in order to hold the secondary electron-emitting dynode 13 at substantially constant potential during the discharge of the sweep capacitor C through the tube 1'. The resultant capacitance of the large by-pass capacitors 8 may be of the order of onetenth of a rnicrofarad to accomplish this purpose, as may the previously mentioned high-frequency by-pass capacitors 57 utilized to maintain the anode 11 of the tube 1 at substantially constant potential.

Each of the un-grounded terminals of the capacitors C through C is connected through corresponding fixed and variable resistors R --R through R R respectively, to a common point P at the upper terminal of the screen-voltage supply potentiometer 14, before described. Through the expedient of having the same circuit that supplies screen potential to the screen-grid electrode 7' and 7 of the tubes 1 and 1, serve to charge the capacitors C through C a single control at 14 can be used to adjust the sweep rate of the circuits associated with both the sweep-generators. There will result at the lower output coupling capacitor C, connected to the anode 11 of the tube 1, an inverted or push-pull sweep voltage V that may be applied to the opposite deflection means to that receiving the sweep voltage V. Horizontal positioning voltage for the sweep may be applied at the terminals 16 through respective resistors 18 and 18.

There will thus result a positive sweep pulse V from the secondary electron-emitting dynode 13 of the tube 1, and a negative sweep pulse V from the anode 11 of the other sweep tube 1 that may be used for push-pull deflection operation. These tubes 1 and 1 produce a linear rise in voltage because they have, in effect, the high dynamic resistance characteristic of a pentode tube, and, therefore, charge the respective sweep capacitors C through C and C through C at an essentially constant rate. The sweep rate is adjustable in the circuit by means of the before-mentioned potentiometer 14 and potentiometers R through R which also fix the screengrid voltages of the sweep tubes 1 and 1'. This is an extremely economical feature in that it enables the use of a single switch Wafer SS to switch in the required sweep capacitors and, at the same time, to vary the voltage to the screen grids of both of the tubes 1 and 1.

Further modifications Will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

l. A sweep circuit having, in combination, a multielectrode electron tube having a control grid, a cathode, and a pair of electrodes serving as an anode and a secondary-electron-emitting electrode, an input circuit connected across the control grid and the cathode for applying input pulses to the tube to cause the tube to conduct, biasing means connected across said control grid and said cathode to permit conduction within the tube only during the application of said input pulses, sweep capacitor means connected in a circuit to one of the said pair of electrodes, and means for holding the other electrode of the said pair at substantially constant potential during the passage of current through the tube and in the said circuit including the capacitor means and the said one electrode of the pair.

2. A sweep circuit having, in combination, a multielectrode electron tube having a control grid, a cathode, and a pair of electrodes serving as an anode and a secondary-electron-emitting electrode, an input circuit connected across the control grid and the cathode for applying input pulses to the tube to cause the tube to conduct, biasing means connected across said control grid and said cathode to permit conduction within the tube only during the application of said input pulses, sweep capacitor means connected in a circuit to the secondary-electron-emitting electrode, and means for holding the anode at substantially constant potential during the passage of current through the tube and in the said circuit including the capacitor means and the secondary-electron-emitting electrode.

3. A sweep circuit having, in combination, a multi-electrode electron tube having a control grid, a cathode, and a pair of electrodes serving as an anode and a secondaryelectron-emitting electrode, an input circuit connected across the control grid and the cathode for applying input pulses to the tube to cause the tube to conduct, biasing means connected across said control grid and said cathode to permit conduction within the tube only during the application of said input pulses, sweep capacitor means connected in a circuit to the secondary-electron-emitting electrode, and means comprising a high-frequency bypass capacitor connected with the anode for holding the same at substantially constant potential during the passage of current through the tube and in the said circuit including the capacitor means and the secondary-electron-emitting electrode.

4. A sweep circuit having, in combination, a multielectrode electron tube having a control grid, a cathode, and a pair of electrodes serving as an anode and a secondary-electron-emitting electrode, an input circuit connected across the control grid and the cathode for applying input pulses to the tube to cause the tube to conduct, biasing means connected across said control grid and said cathode to permit conduction within the tube only during the application of said input pulses, sweep capacitor means connected in a circuit to the anode electrode, and means for holding the secondary-electron-emitting electrode at substantially constant potential during the passage of current through the tube and in the said circuit including the capacitor means and the anode.

5. A sweep circuit having, in combination, a multielectrode electron tube having a control grid, a cathode, and a pair of electrodes serving as an anode and a secondary-electron-emitting electrode, an input circuit connected across the control grid and the cathode for applying input pulses to the tube to cause the tube to conduct, biasing means connected across said control grid and said cathode to permit conduction within the tube only during the application of said input pulses, sweep capacitor means connected in a circuit to the anode electrode, and means comprising a relatively large by-pass capacitor connected with the secondary-electron-emitting electrode for holding the same at substantially constant potential during the passage of current through the tube and in the said circuit including the capacitor means and the anode.

6. A circuit for generating a pair of matched sweep signals having, in combination, a pair of multi-electrode electron tubes each having a control grid, a cathode, and a pair of electrodes serving as an anode and a secondaryelectron-emitting electrode, an input circuit connected across the control grid and the cathode of both tubes for applying input pulses to both tubes substantially simultaneously to cause both tubes to conduct, biasing means connected across the control grid and the cathode of each tube to permit conduction within the tubes only during the application of said input pulses, a pair of sweep capacitor means one of which is connected in a circuit with one of the said pair of electrodes of each tube, means for holding the other electrode of the said pair of electrodes of each tube at substantially constant potential during the passage of current through each tube and in the said circuit including the capacitor means and the said one electrode of the pair of electrodes of each tube, and means for extracting substantially simultaneous sweep outputs from the said one electrode of each of the pair of tubes.

7. A circuit for generating a pair of sweep signals each being substantially a mirror image of the other, having, in combination, a pair of multi-electrode electron tubes each having an anode, a secondary-electron-emitting electrode, a control grid and a cathode; an input circuit connected across the control grid and the cathode of both tubes for applying input pulses to both tubes substantially simultaneously to cause both tubes to conduct, biasing means connected across the control grid and the cathode of each tube to permit conduction within the tubes only during the application of said input pulses; a pair of sweep capacitor means, one of which is connected in a circuit with the anode of one tube and the other of which is connected in a circuit with the secondary-electron-emitting electrode of the other tube; means for holding the secondary-electron-emitting electrode of the said one tube and the anode of the said other tube at substantially constant potential during the passage of current through each tube and in each of the said circuits including the capacitor means; and means for extracting substantially simultaneous sweep output signals from the anode of the said first tube and the secondary-electron-emitting electrode of said other tube.

8. A sweep circuit as claimed in claim 7 and in which the holding means comprises a high-frequency by-pass capacitor connected with the anode of the said other tube.

9. A sweep circuit as claimed in claim 7 and in which the holding means comprises a relatively large by-pass capacitor connected with the secondary-electron-emitting electrode of the said one tube.

10. A sweep circuit as claimed in claim 7 and in which each of the tubes is provided with a screen grid and a common source of screen potential, and the sweep capacitor means of the said one tube is energized by the said source of screen potential.

References Cited in the file of this patent UNITED STATES PATENTS 2,294,782 Iaeobsen Sept. 1, 1942 2,456,754 Sziklai Dec. 21, 1948 2,497,640 Van Weel Feb. 14, 1950 2,509,998 Van Der Mark et a1. May 20, 1950 2,954,466 Campbell Sept. 27, 1960 FOREIGN PATENTS 375,238 Italy Sept. 28, 1939 279,507 Italy Mar. 28, 1940 

